Method of adding activated carbon in water purification and method of water purification

ABSTRACT

When a raw water to be filtered c is fed from a raw water tank  11  reservoiring a raw water (water to be treated) to a membrane module by a raw water pump P 1 , an activated carbon raw material supplied from an activated carbon tank is milled together with water to be mixed by a wet milling device, and added and mixed into the raw water tank as an aqueous suspension containing activated carbon fine particles having an average particle size of 0.1 μm to 10 μm, thus producing the raw water to be filtered (activated carbon-containing water to be treated). The raw water to be filtered (activated carbon-containing water to be treated) is filtered by the membrane module at a subsequent step, thereby obtaining a purified water.

TECHNICAL FIELD

The present invention relates to a method of adding activated carbon inwater purification and a method of water purification to improve qualityof purified water by adsorption of the activated carbon.

BACKGROUND ART

A water treatment apparatus, for example, utilizing activated carbon asshown in FIG. 2 has been known as an apparatus to purify river water toobtain purified water of high quality. In a technique disclosed here,water to be treated is fed from a raw water tank 11 reservoiring a rawwater (a) through passages 12, 13 by a raw water pump P1, a circulationpump P2 to a membrane module 14 where suspended solids (SS) are removed,thereby a purified water (b) is obtained. In case of the apparatus shownas example, the apparatus is configured to return water to be treatedthrough a passage 15 for circulation.

Furthermore, in the instance shown in this figure, organic substancessuch as abnormal taste and odor causing materials, coloring materialsand the trihalomethane precursors in the raw water (a) is removed byadding, from powder activated carbon injection means 16, activatedcarbon of ultra-fine particle powder having a particle size of 0.01 μmto 10 μm, instead of activated carbon powder having a particle size ofabout 18 μm which has heretofore been used.

However, in such a known method, there has been used activated carbon ofultra-fine particle powder having been milled in advance by a certainmethod to have a particle size of 0.01 μm to 10 μm, however, suchactivated carbon of ultra-fine particle powder in itself is apt toaggregate and easily forms a secondary aggregate; thus, there is aproblem that effects of careful selection of ultra-fine particle powderare not sufficiently attained. Moreover, there is also such adisadvantage that fine particle powder causes dust in handling.

The present invention has been made to solve the problems describedabove, and is intended to provide a method of adding activated carbon ina water purification treatment and method of water purificationtreatment, wherein secondary aggregation of the activated carbonultra-fine particles can be suppressed to make full use of itsadsorption performance and the dusting of activated carbon fineparticles during handling can be prevented, in the water purificationtreatment by which the quality of purified water is improved byutilizing the adsorption of the activated carbon.

DISCLOSURE OF THE INVENTION

The present invention has been made to achieve the aforementionedobjects, and there is provided according to the present invention amethod of adding activated carbon in water purification treatment byadding activated carbon to water to be treated to purify the water to betreated, characterized in that an aqueous suspension containingactivated carbon fine particles having an average particle size of 0.1μm to 10 μm obtainable by wet milling of the particles of the activatedcarbon is added to water to be treated.

Furthermore, according to the present invention, there is provided awater treatment method of purifying a water to be treated by use ofactivated carbon, characterized by adding, to water to be treated, anaqueous suspension containing the activated carbon fine particles havingan average particle size of 0.1 μm to 10 μm obtainable by wet milling ofthe particles of the activated carbon, and by further subjecting theobtained activated carbon-containing water to be treated to a membraneseparation treatment.

In the present invention, a concentration of activated carbon in theaqueous suspension containing activated carbon fine particles ispreferably 0.1 mass percent to 10 mass percents.

Furthermore, a milling machine is preferably installed by attaching itto a passage of the water to be treated or to a tank reservoiring waterto be treated, so that activated carbon particles are subjected to wetmilling by the milling machine.

The method of adding activated carbon in the water purificationtreatment and the method of water purification treatment according tothe present invention are constructed as described above, so that thesecondary aggregation of activated carbon fine particles can besuppressed, thereby its adsorption performance can be fully utilized andthe dusting of activated carbon fine particles can be prevented.Further, a cheap activated carbon raw material can be used, and the costreduction is attained therefore. Still further, a working environmentcan be improved. Thus, the present invention has a great industrialvalue as a method of adding activated carbon in the water purificationtreatment and the method of water purification treatment capable ofsolving the conventional problems.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram of essential parts of a water treatmentapparatus to explain an activated carbon addition method of the presentinvention; and

FIG. 2 is a flow diagram of a conventional water treatment apparatususing activated carbon.

BEST MODE FOR CARRYING OUT THE INVENTION

A best mode for carrying out a method of adding activated carbon inwater purification and a water treatment method of the present inventionwill hereinafter be described in detail referring to the drawings.

As shown in FIG. 1, in the present invention, when a raw water to befiltered (c) is fed from a raw water tank 11 reservoiring a raw water(water to be treated) (a) such as river water to a membrane module (notshown) by a raw water pump P1, an activated carbon raw material suppliedfrom an activated carbon tank 21 is put into a water to be mixed (d),and then milled by a wet milling device 22, and added and mixed into theraw water tank 11 as an aqueous suspension containing activated carbonfine particles having an average particle size of 0.1 μm to 10 μm, thusproducing the raw water to be filtered (activated carbon-containingwater to be treated) (c). The features of the present invention lies inthe point that the activated carbon fine particles thus milled are usedin a state co-existing with water without undergoing a dried state.

Here, the average particle size of the activated carbon fine particlesused in the present invention means a volume mean diameter, and isobtained by measurement using a laser diffraction scattering method.

The raw water to be filtered (activated carbon-containing water to betreated) (c) to which such activated carbon fine particles are added isfiltered by the membrane module at a subsequent step as in the caseshown in FIG. 2, thereby allowing a purified water (b) to be obtained.In this case, the aqueous suspension containing activated carbon fineparticles obtainable by the wet milling device 22 is added into the rawwater tank 11, but may be injected directly into a supply passage of theraw water (water to be treated) (a) to produce the raw water to befiltered (activated carbon-containing water to be treated) (c).

The average particle size of the activated carbon fine particles used inthe present invention is within a range of 0.1 μm to 10 μm as describedabove, and is preferably in a range of 0.5 μm to 10 pn. When the averageparticle size is below 0.1 μm, for example, when a microfiltration (MF)membrane treatment is combined, the activated carbon fine particles aredifficult to separate by the MF membrane treatment, and when the averageparticle size is above 10 μm, the full advantage of the presentinvention cannot be attained effectively since one may use commerciallyavailable products having an average particle size of above 10 μm.Moreover, when the average particle size is 0.5 μm or above, completecapture can be achieved by an MF membrane surface, so that the activatedcarbon fine particles do not penetrate into the membrane, thereby anefficient membrane filtration can be attained.

According to the present invention, the activated carbon raw material issubjected to wet milling, and the obtained activated carbon fineparticles are dispersed into the aqueous suspension and added in a statenot to cause secondary aggregation, so that an adsorption effect oforganic matters and the like in the raw water can be sufficientlydisplayed. Further, the commercially available products having anaverage particle size of above 10 μm can be used for the activatedcarbon raw material, which is an advantage in that it is easy topurchase and cheap in the raw material costs. Also, there is anadvantage that no dusting problem occurs since the activated carbon fineparticles are handled as the aqueous suspension in the presentinvention, and that the used activated carbon raw material has a largeparticle size to cause no powder dust and is thus easy to handle.

The preferable particle size of the activated carbon fine particles usedin the present invention has been as described above, but there is alsoan advantage that an adjustment can be properly made to have an optimumvalue for a particle size obtained by adjusting an operating conditionof the wet milling device 22 in dependence upon a purification objectand upon a filtration size of a filtration membrane of the membranemodule at the subsequent step (e.g., an adjustment is made in dependenceupon a use target and upon the purpose; for example, the particle sizeis reduced when adsorption properties are considered by priority, or theparticle size is made larger when the efficiency of biological activatedcarbon is required).

It is to be noted that the membrane separation treatment (membranemodule) used in the present invention includes, for example, a monolithtype ceramic membrane as a preferred example.

Furthermore, the wet milling device used in the present invention is notspecifically limited as long as it is of a type capable of millingactivated carbon after putting it into water to be mixed (d) fordispersion, but the wet milling device can include, as a preferredexample, a fine milling device such as a roll ball mill, an oscillatingball mill or an attriter mill having a ball or a rod as a millingmedium.

Still further, a concentration of the activated carbon in the aqueoussuspension containing the activated carbon fine particles used in thepresent invention is preferably within a range of 0.1 mass percent to 10mass percents. If it is below 0.1%, the raw water to be filtered (c) isdiluted, and treatment efficiency in the membrane module at thesubsequent step may decrease. If it is above 10%, the activated carbonfine particles may easily cause the secondary aggregation.

EXAMPLES

An example of the present invention and comparative examples are shownbelow in Table 1. In Table 1, activated carbon fine particles obtainedby the present invention were used in the example. In the example of thepresent invention in which there was used a test solution containingorganic impurities at a predetermined concentration, an addition amountof the activated carbon fine particles was regarded as 100 when thecontained organic impurities could be removed therefrom, and inComparative Examples 1 and 2, addition amounts of activated carbonswhich were required to obtain the same effect as the above level of 100are shown as relative amounts in Table 1.

According to these results, it was found that the present inventioncould provide a similar effect in addition amounts of 67% and 33% of theamounts of the activated carbons in Comparative Examples 1 and 2,respectively, and the present invention could sufficiently demonstratean effect of milling of the activated carbon. TABLE 1 Addition amountKind of activated carbon Example 100 Activated carbon wet milling:particle size (average) 1.0 μm Comparative 150 Power dried for 24 hoursExample 1 after wet milling at a particle size 1.0 μm Comparative 300Commercially available Example 2 product of particle size of 15 μm

INDUSTRIAL APPLICABILITY

The present invention is preferably utilized in various kinds ofindustrial fields where a water to be treated such as a river water or acertain industrial water needs to be efficiently purified to obtainpurified water of high quality.

1. A method of adding activated carbon in water purification treatmentby adding activated carbon to water to be treated to purify water to betreated, characterized in that an aqueous suspension containingactivated carbon fine particles having an average particle size of 0.1μm to 10 μm obtainable by wet milling of the particles of the activatedcarbon is added to the water to be treated.
 2. The addition method ofactivated carbon in the water purification treatment according to claim1, wherein a concentration of the activated carbon in an aqueoussuspension containing the activated carbon fine particles is 0.1 masspercent to 10 mass percents.
 3. The addition method of activated carbonin the water treatment according to claim 1, wherein a milling machineis installed by attaching to a passage of the water to be treated or toa tank reservoiring water to be treated, so that the activated carbonparticles are subjected to wet milling by the milling machine.
 4. Awater treatment method of purifying water to be treated by use ofactivated carbon, characterized by adding, to water to be treated, anaqueous suspension containing activated carbon fine particles having anaverage particle size of 0.1 μm to 10 μm obtainable by wet milling ofthe particles of the activated carbon, and by further subjecting anobtained activated carbon-containing water to be treated to a membraneseparation treatment.
 5. The water treatment method according to claim4, wherein a concentration of activated carbon in the aqueous suspensioncontaining the activated carbon fine particles is 0.1 mass percent to 10mass percents.
 6. The water treatment method according to claim 4,wherein milling machine is installed by attaching to a passage of waterto be treated or to a tank reservoiring water to be treated, so that theactivated carbon particles are subjected to wet milling by the millingmachine.
 7. The addition method of activated carbon in the watertreatment according to claim 2, wherein a milling machine is installedby attaching to a passage of the water to be treated or to a tankreservoiring water to be treated, so that the activated carbon particlesare subjected to wet milling by the milling machine.
 8. The watertreatment method according to claim 5, wherein milling machine isinstalled by attaching to a passage of water to be treated or to a tankreservoiring water to be treated, so that the activated carbon particlesare subjected to wet milling by the milling machine.